U.S. patent number 10,023,417 [Application Number 15/170,310] was granted by the patent office on 2018-07-17 for sheet post-processing apparatus and image forming system.
This patent grant is currently assigned to Ricoh Company, Ltd.. The grantee listed for this patent is Masaaki Kawasaki, Masanobu Kimata, Ryohei Morisaki, Norihiko Murakami, Maki Nishide, Hidefumi Shibata. Invention is credited to Masaaki Kawasaki, Masanobu Kimata, Ryohei Morisaki, Norihiko Murakami, Maki Nishide, Hidefumi Shibata.
United States Patent |
10,023,417 |
Shibata , et al. |
July 17, 2018 |
Sheet post-processing apparatus and image forming system
Abstract
A sheet post-processing apparatus includes: a sheet stack tray;
a rear-end-position regulating member, against which a rear end of
the sheet on the tray is butted to align a position of the sheet in
a sheet conveying direction to the stack tray, the rear end of the
sheet being a rear end in the conveying direction; and a roller
member that comes in contact with an upper surface of the sheet
conveyed to an upper side of the tray, before the sheet is stacked
on a stacking surface on the tray, and conveys the sheet stacked on
the stacking surface toward the rear-end-position regulating
member, wherein a rotation speed before stacking is set to be
smaller than a rotation speed after stacking, and the rotation
speed of before stacking is greater than zero.
Inventors: |
Shibata; Hidefumi (Kanagawa,
JP), Kimata; Masanobu (Kanagawa, JP),
Kawasaki; Masaaki (Kanagawa, JP), Morisaki;
Ryohei (Kanagawa, JP), Murakami; Norihiko
(Kanagawa, JP), Nishide; Maki (Kanagawa,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Shibata; Hidefumi
Kimata; Masanobu
Kawasaki; Masaaki
Morisaki; Ryohei
Murakami; Norihiko
Nishide; Maki |
Kanagawa
Kanagawa
Kanagawa
Kanagawa
Kanagawa
Kanagawa |
N/A
N/A
N/A
N/A
N/A
N/A |
JP
JP
JP
JP
JP
JP |
|
|
Assignee: |
Ricoh Company, Ltd. (Tokyo,
JP)
|
Family
ID: |
57450800 |
Appl.
No.: |
15/170,310 |
Filed: |
June 1, 2016 |
Prior Publication Data
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|
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Document
Identifier |
Publication Date |
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US 20160355364 A1 |
Dec 8, 2016 |
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Foreign Application Priority Data
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Jun 3, 2015 [JP] |
|
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2015-113136 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03G
15/6541 (20130101); B65H 31/3027 (20130101); B65H
31/02 (20130101); B65H 31/38 (20130101); B65H
31/36 (20130101); G03G 15/6582 (20130101); B65H
2511/152 (20130101); B65H 2403/942 (20130101); B65H
2301/4212 (20130101); B65H 2511/30 (20130101); B65H
2301/4213 (20130101); B65H 2511/13 (20130101); B65H
2553/612 (20130101); B65H 2513/53 (20130101); G03G
2215/00822 (20130101); B65H 2405/11151 (20130101); B65H
2513/11 (20130101); B65H 2511/17 (20130101); B65H
2404/1521 (20130101); B65H 2404/723 (20130101); B65H
2801/27 (20130101); B65H 2513/108 (20130101); B65H
2511/152 (20130101); B65H 2220/03 (20130101); B65H
2511/30 (20130101); B65H 2220/01 (20130101); B65H
2513/53 (20130101); B65H 2220/02 (20130101); B65H
2513/11 (20130101); B65H 2220/02 (20130101); B65H
2220/11 (20130101); B65H 2511/17 (20130101); B65H
2220/03 (20130101); B65H 2513/108 (20130101); B65H
2220/02 (20130101); B65H 2511/13 (20130101); B65H
2220/01 (20130101) |
Current International
Class: |
B65H
31/02 (20060101); G03G 15/00 (20060101); B65H
31/38 (20060101); B65H 31/30 (20060101); B65H
31/36 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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11-060026 |
|
Mar 1999 |
|
JP |
|
2007-153454 |
|
Jun 2007 |
|
JP |
|
2009-227468 |
|
Oct 2009 |
|
JP |
|
2013-189272 |
|
Sep 2013 |
|
JP |
|
Primary Examiner: Severson; Jeremy R
Attorney, Agent or Firm: Harness, Dickey & Pierce,
P.L.C.
Claims
What is claimed is:
1. A sheet post-processing apparatus comprising: a stack tray
configured to stack a sheet thereon; a rear-end-position regulating
member, against which a rear end of the sheet stacked on the stack
tray is butted, the rear-end-position regulating member being
configured to align a position of the sheet in a conveying
direction, the rear end of the sheet being a rear end in the
conveying direction; a roller member configured to, contact an
upper surface of the sheet, if the sheet is conveyed to an upper
side of the stack tray, before the sheet is stacked on a stacking
surface on the stack tray, and convey the sheet stacked on the
stacking surface toward the rear-end-position regulating member;
and a deflection detector configured to detect deflection of a
sheet caused by conveyance by the roller member.
2. The sheet post-processing apparatus according to claim 1,
further comprising: a butting member that is configured to move
into contact with or away from the stacking surface, rotate to
convey a sheet conveyed toward the rear-end-position regulating
member by the roller member, and cause the sheet to butt against
the rear-end-position regulating member; a sheet detector arranged
between the roller member and the butting member and configured to
detect the sheet.
3. The sheet post-processing apparatus according to claim 2,
further comprising: a paper ejection tray configured to stack a
sheet discharged from the stack tray; and a returning member
configured to rotate to return a sheet discharged on the paper
ejection tray to an upstream side in a discharging direction.
4. An image forming system comprising: an image forming apparatus
that forms an image on a sheet based on image information; and a
sheet post-processing apparatus, the sheet post-processing
apparatus including a stack tray configured to stack the sheet
thereon, a rear-end-position regulating member, against which a
rear end of the sheet stacked on the stack tray is butted to align
a position of the sheet in a conveying direction, the rear end of
the sheet being a rear end in the conveying direction, and a roller
member configured to contact an upper surface of the sheet, if the
sheet is conveyed to an upper side of the stack tray, before the
sheet is stacked on a stacking surface on the stack tray, convey
the sheet stacked on the stacking surface toward the
rear-end-position regulating member; and a deflection detector
configured to detect deflection of a sheet caused by conveyance by
the roller member.
5. A method of operating a sheet post-processing apparatus, the
sheet post processing apparatus including a stack tray configured
to stack a sheet thereon, a rear-end-position regulating member,
against which a rear end of the sheet stacked on the stack tray is
butted, the rear-end-position regulating member being configured to
align a position of the sheet in a conveying direction, the rear
end of the sheet being a rear end in the conveying direction, and a
roller member configured to, contact an upper surface of the sheet,
if the sheet is conveyed to an upper side of the stack tray, before
the sheet is stacked on a stacking surface on the stack tray and
convey the sheet stacked on the stacking surface toward the
rear-end-position regulating member, the method comprising:
rotating the roller member at a first rotation speed while the
roller member is in contact with the sheet before the rear end of
the sheet lands on the stacking surface, the first rotation speed
being less than a second rotation speed, the first rotation speed
being greater than zero; and rotating the roller member at the
second rotation speed when the roller member conveys the sheet to
the rear-end-position regulating member while the sheet is on the
stacking surface.
6. The method according to claim 5, further comprising: moving the
roller member into contact with the sheet while the roller member
is in a non-rotating state, wherein the rotating the roller member
at the first rotation speed begins a time t1 before the roller
member contacts the stacking surface via the sheet.
7. The method according to claim 6, wherein the rotating the roller
member at the second rotation begins a time t2 after the contact of
the roller member with the stacking surface via the sheet.
8. The method according to claim 7, further comprising: rotating by
the roller member at a third rotation speed during a time t3 before
the end of the time t2, the third rotation speed being higher than
the first rotation speed and lower than the second rotation
speed.
9. The method according to claim 8, further comprising: changing
one of the time t1, the time t2, and the time t3 based on a number
of stacked sheets.
10. The method according to claim 8, further comprising: changing
one of the time t1, the time t2, and the time t3 based on a sheet
type.
11. The method according to claim 8, further comprising: detecting,
by a stack height detector, a height of a stack of sheets on the
stack tray; and changing one of the time t1, the time t2, and the
time t3 based on detection information obtained from the stack
height detector, wherein the sheet post-processing apparatus
includes the stack height detector.
12. The method according to claim 7, further comprising: changing
one of the time t1 and the time t2 based on a number of stacked
sheets.
13. The method according to claim 7, further comprising: changing
one of the time t1 and the time t2 based on a sheet type.
14. The method according to claim 7, further comprising: detecting,
by a stack height detector, a height of a stack of sheets on the
stack tray; and changing one of the time t1, and the time t2 based
on detection information obtained from the stack height detector,
wherein the sheet post-processing apparatus includes the stack
height detector.
15. The method according to claim 6, further comprising: changing
the time t1 based on a number of stacked sheets.
16. The method according to claim 6, further comprising: changing
the time t1 based on a sheet type.
17. The method according to claim 6, further comprising: detecting,
by a stack height detector, a height of a stack of sheets on the
stack tray; and changing the time t1, based on detection
information obtained from the stack height detector, wherein the
sheet post-processing apparatus includes the stack height
detector.
18. The method according to claim 5, wherein changing at least one
of the first rotation speed and the second rotation speed based on
a sheet type.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. .sctn. 119
to Japanese Patent Application No. 2015-113136 filed in Japan on
Jun. 3, 2015. The contents of which are incorporated herein by
reference in their entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sheet post-processing apparatus
and an image forming system.
2. Description of the Related Art
For example, there is a known sheet post-processing apparatus that
temporarily stacks, on a stack tray, sheets conveyed from an image
forming apparatus, performs a binding process on a sheet bundle
that is a stack of a predetermined number of sheets, and then
discharges the sheet bundle.
A sheet conveyed onto the stack tray comes in contact with a roller
member that rotates in a direction in which the sheet is fed back
toward an upstream side in a conveying direction, so that the
motion of the sheet is damped and the sheet falls onto the stack
tray. Subsequently, the sheet is conveyed to the upstream side in
the conveying direction on the stack tray by the roller member and
a rear end of the sheet butts against a rear-end-position
regulating member, so that the sheet is aligned in the conveying
direction.
The rotation speed of the roller member is constant without a
change between when the sheet falls and when the sheet is conveyed
to the rear-end-position regulating member.
Japanese Patent Laid-open Publication No. 2009-227468 discloses a
technology, in which the speed of a rotation member for conveying a
sheet to a rear-end-position regulating member is reduced relative
to the rotation speed of a roller member for causing a sheet to
fall onto a stack tray, in order to prevent buckling that occurs
when the sheet is excessively conveyed backward.
The state of a sheet that is falling onto a stacking surface of the
stack tray is unstable in the air. Therefore, if a conveying force
is applied to the sheet by the roller member, a landing position of
the sheet fluctuates.
If the rear end of the landed sheet is too close to the
rear-end-position regulating member, the sheet is excessively
conveyed at the time of rear-end butting, and sheet buckling
occurs.
In contrast, if the rear end of the landed sheet is too far from
the rear-end-position regulating member, the rear end of the sheet
may not be conveyed to the rear-end-position regulating member, and
a binding failure may occur.
In Japanese Patent Laid-open Publication No. 2009-227468, the
influence of the roller member while the sheet is falling onto the
stack tray is not considered.
In view of the above circumstances, there is a need to provide a
sheet post-processing apparatus capable of stabilizing a landing
state of a sheet on a stack tray, and contributing to sheet
alignment accuracy and post-processing accuracy.
SUMMARY OF THE INVENTION
It is an object of the present invention to at least partially
solve the problems in the conventional technology.
According to exemplary embodiments of the present invention, there
is provided a sheet post-processing apparatus comprising: a stack
tray for stacking a sheet; a rear-end-position regulating member,
against which a rear end of the sheet stacked on the stack tray is
butted to align a position of the sheet in a conveying direction in
which the sheet is conveyed toward the stack tray, the rear end of
the sheet being a rear end in the conveying direction; and a roller
member that comes in contact with an upper surface of a sheet
conveyed to an upper side of the stack tray, before the sheet is
stacked on a stacking surface on the stack tray, and conveys the
sheet stacked on the stacking surface toward the rear-end-position
regulating member, wherein a rotation speed before stacking, which
is a rotation speed of the roller member when the roller member is
in contact with the sheet while the rear end of the sheet in the
conveying direction is not landed on the stacking surface, is set
to be smaller than a rotation speed after stacking, which is a
rotation speed of the roller member when the roller member conveys
the sheet to the rear-end-position regulating member while the
sheet is stacked on the stacking surface, and the rotation speed of
before stacking is greater than zero.
Exemplary embodiments of the present invention also provide an
image forming system comprising: an image forming apparatus that
forms an image on a sheet based on image information; and a sheet
post-processing apparatus, wherein the sheet post-processing
apparatus comprises; a stack tray for stacking the sheet; a
rear-end-position regulating member, against which a rear end of
the sheet stacked on the stack tray is butted to align a position
of the sheet in a conveying direction in which the sheet is
conveyed toward the stack tray, the rear end of the sheet being a
rear end in the conveying direction; and a roller member that comes
in contact with an upper surface of the sheet conveyed to an upper
side of the stack tray, before the sheet is stacked on a stacking
surface on the stack tray, and conveys the sheet stacked on the
stacking surface toward the rear-end-position regulating member,
wherein a rotation speed before stacking, which is a rotation speed
of the roller member when the roller member is in contact with the
sheet while the rear end of the sheet in the conveying direction is
not landed on the stacking surface, is set to be smaller than a
rotation speed after stacking, which is a rotation speed of the
roller member when the roller member conveys the sheet to the
rear-end-position regulating member while the sheet is stacked on
the stacking surface, and the rotation speed of before stacking is
greater than zero.
The above and other objects, features, advantages and technical and
industrial significance of this invention will be better understood
by reading the following detailed description of presently
preferred embodiments of the invention, when considered in
connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic configuration diagram of an image forming
system according to a first embodiment of the present
invention;
FIG. 2 is a diagram illustrating main parts in a state in which a
sheet is conveyed to a staple tray;
FIG. 3 is a diagram illustrating the main parts in a state in which
a tapping roller starts to rotate from the state illustrated in
FIG. 2;
FIG. 4 is a diagram illustrating the main parts in a state in which
a rotation roller of the tapping roller comes in contact with the
sheet;
FIG. 5 is a diagram illustrating the main parts in a state in which
the sheet is stacked on the staple tray and is conveyed toward a
rear end stopper by the rotation roller;
FIG. 6 is a timing diagram illustrating timings of setting a
rotation speed of the rotation roller before stacking and a
rotation speed of the rotation roller after stacking;
FIGS. 7A and 7B are diagrams illustrating an operation of aligning
the rear end of a sheet on the staple tray;
FIG. 8 is a timing diagram illustrating timings of setting a
rotation speed of a rotation roller before stacking and a rotation
speed of the rotation roller after stacking according to a second
embodiment of the present invention;
FIGS. 9A to 9F are diagrams illustrating a deflection detection
operation and a rear end alignment operation according to a third
embodiment of the present invention;
FIGS. 10A and 10B are diagrams illustrating the deflection
detection operation and the rear end alignment operation on a
second sheet according to the third embodiment;
FIGS. 11A to 11C are diagrams illustrating a deflection detection
operation and a rear end alignment operation according to a fourth
embodiment of the present invention;
FIGS. 12A and 12B are diagrams illustrating discharge to a paper
ejection tray and a rear end alignment operation on the paper
ejection tray according to a fifth embodiment of the present
invention;
FIG. 13 is a perspective view illustrating a sheet bundle aligned
on the staple tray;
FIG. 14 is a plan view illustrating an initial state of the rear
end alignment operation of on a first sheet on the staple tray;
FIGS. 15A to 15E are diagrams illustrating the rear end alignment
operation and a lateral alignment operation performed by jogger
fences; and
FIGS. 16A to 16D are diagrams illustrating a punching operation
performed by a punching unit.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Exemplary embodiments of the present invention will be described
below with reference to the drawings.
FIG. 1 to FIG. 7B illustrate a first embodiment.
An overview of a configuration of an image forming system according
to the first embodiment will be described based on FIG. 1. An image
forming system 2 includes an image forming apparatus 4 and a sheet
post-processing apparatus 6 that is arranged on a sheet discharge
side of the image forming apparatus 4.
The image forming apparatus 4 is a conventionally-known
electrophotography image forming apparatus, and is configured to
form an electrostatic latent image based on image information on an
image bearer by an exposing unit, develop the electrostatic latent
image by a developing unit, eventually transfer the developed toner
image to a recording medium (hereinafter, referred to as a sheet or
paper), and fix the image by a fixing unit.
The sheet post-processing apparatus 6 may be integrated with the
image forming apparatus 4 or may be detachably connected to the
image forming apparatus 4.
An image-formed sheet discharged from the image forming apparatus 4
enters a first conveying path 10 of the sheet post-processing
apparatus 6 through a connection port 8. On the first conveying
path 10, an entrance roller pair 12 and an entrance sensor 14 are
arranged, and the entrance sensor 14 detects that a sheet is
conveyed into the sheet post-processing apparatus 6.
On the downstream side of the entrance roller pair 12, a punching
unit 16 that punches a hole in the sheet is arranged. On the
downstream side of the punching unit 16, a conveying roller pair 18
is arranged.
The downstream side of the conveying roller pair 18 is bifurcated
into a second conveying path 20 extending upward and a third
conveying path 22 as an extended path of the first conveying path
10.
In a bifurcation area of the second conveying path 20 and the third
conveying path 22, a first bifurcating claw 24 is provided. By
controlling rotation of the first bifurcating claw 24, a sheet is
selectively guided to one of the conveying paths.
The sheet guided to the second conveying path 20 is conveyed by a
conveying roller pair 26, and discharged to a proof tray 30 by a
paper ejection roller pair 28.
A fourth conveying path 32 is branched from the third conveying
path 22. By controlling rotation of a second bifurcating claw 34, a
sheet is selectively guided to the fourth conveying path 32. The
sheet guided to the fourth conveying path 32 is conveyed by a
pre-stack roller pair 36.
On the third conveying path 22, an intermediate conveying roller
pair 40 for conveying a sheet to an end binding unit 38 is
arranged. In the vicinity of the upstream side of the intermediate
conveying roller pair 40, an intermediate conveying sensor 42 that
detects a sheet is arranged.
The sheet is ejected on a staple tray 44, which is a stack tray, by
the intermediate conveying roller pair 40. A tapping roller 46 as a
roller member is arranged above the staple tray 44. A rear end
stopper 48 as a rear-end-position regulating member is arranged on
the upstream side of the staple tray 44 in a sheet conveying
direction.
The tapping roller 46 as one of aligning members performs a
pendulum motion to thereby come in contact with a sheet, drop the
sheet onto the staple tray 44 with high landing accuracy, and
convey the sheet toward the rear end stopper 48.
A rear end of the sheet conveyed by the tapping roller 46 is butted
against the rear end stopper 48 by a returning roller 50 as a
butting member that is another one of the aligning members, so that
the position of a sheet bundle in the conveying direction is
aligned. The returning roller 50 is capable of coming in contact
with and away from a stacking surface.
The rear end of the sheet means a rear end of a sheet in the
conveying direction when the sheet is conveyed toward the staple
tray 44.
On the staple tray 44, a pair of jogger fences 52 is provided. The
jogger fences 52 move back and forth in a sheet width direction
(lateral direction) perpendicular to the sheet conveying direction
and align the position of a sheet ejected on the staple tray 44 in
the sheet width direction.
Through the above-described two operations, sheets ejected on the
staple tray 44 are stacked in an aligned manner. As for the aligned
sheet bundle, in a staple mode, an end binding stapler 54 moves in
the sheet width direction and binds an appropriate portion in a
lower edge area of the aligned sheet bundle.
The sheet bundle (paper bundle) subjected to a binding process is
discharged onto a paper ejection tray 60 by a discharging claw 58
that is moved by a belt conveying unit 56. The belt conveying unit
56 includes supporting rollers 56a and 56b and a belt 56c.
When the sheet bundle is discharged, the sheet bundle is stably
discharged by being sandwiched by a paper ejection roller 62 and a
driven roller 64.
With reference to FIGS. 2 to 5, a sheet stack operation in the
staple mode will be described.
As illustrated in FIG. 2, the tapping roller 46 includes a rotation
roller 46a and can rotate in a vertical direction by using a shaft
46b as a fulcrum. Rotation of the rotation roller 46a is
arbitrarily controlled.
An image-formed sheet 66 conveyed from the image forming apparatus
4 passes through the intermediate conveying roller pair 40 and is
conveyed to the upper side of the staple tray 44.
At a timing at which the intermediate conveying sensor 42 detects a
rear end of the sheet 66, the tapping roller 46 starts to perform a
tapping operation.
That is, as illustrated in FIG. 3, the tapping roller 46 rotates
downward toward the stacking surface of the staple tray 44 while
the rotation roller 46a is in a non-rotating state.
The stacking surface indicates a stacking surface of the staple
tray 44 when a sheet is not present on the staple tray 44, and
indicates a surface of the topmost sheet when sheets are present on
the staple tray 44.
As illustrated in FIG. 4, the rotation roller 46a comes in contact
with an upper surface of a sheet along with the rotation of the
tapping roller 46. The rotation roller 46a comes in contact with
the sheet 66 while the rotation roller 46a is in a non-rotating
state, and then starts to rotate counterclockwise before coming in
contact with the stacking surface of the staple tray 44 via the
sheet 66.
As illustrated in FIG. 5, after the rotation roller 46a comes in
contact with the stacking surface of the staple tray 44 via the
sheet 66, that is, after the sheet 66 is stacked on the staple tray
44, the sheet 66 is conveyed toward the rear end stopper 48 by the
rotation roller 46a.
The above-described stack operation will be described in detail
below with reference to a timing diagram.
As illustrated in FIG. 6, after the rotation roller 46a comes in
contact with the sheet 66, the rotation roller 46a is rotated at a
rotation speed a rpm (revolutions per minute), which is a rotation
speed before stacking, a predetermined time t1 ms (milliseconds)
before the rotation roller 46a comes in contact with (lands on) the
stacking surface of the staple tray 44 via the sheet 66.
The rotation speed before stacking is a rotation speed of the
rotation roller 46a when the rotation roller 46a is in contact with
a sheet while the rear end of the sheet in the conveying direction
is not landed on the stacking surface.
After a predetermined time t2 (ms) since the landing of the
rotation roller 46a on the staple tray 44 via the sheet 66, the
rotation roller 46a is rotated at a rotation speed b (rpm), which
is a rotation speed after stacking.
It is assumed that the rotation speed b (rpm) is a rotation speed
with a conveying force to cause the rotation roller 46a to guide
the sheet 66 to the rear end stopper 48.
It is also assumed that the rotation speed a is lower than the
rotation speed b and has a value grater than 0 (rpm) in order to
prevent a sheet from adhering to the stacking surface of the staple
tray 44.
That is, the rotation speed a is a speed to apply, to the sheet 66
in an unstable state in the air above the staple tray 44, the
minimum rotation force needed to prevent the sheet from adhering to
the stacking surface. Consequently, it becomes possible to cause
the sheet 66 to stably land on the staple tray 44.
As illustrated in FIG. 7A, the sheet 66 landed and stacked on the
staple tray 44 is conveyed toward the rear end stopper 48 by the
rotation roller 46a that rotates at the rotation speed b.
Subsequently, as illustrated in FIG. 7B, the sheet 66 butts against
the rear end stopper 48 due to the conveyance by the rotation
roller 46a and the returning roller 50, and the position of the
sheet 66 in the conveying direction is aligned.
The above-described stack operation is repeated for each sheet
conveyed by the intermediate conveying roller pair 40. Fluctuation
of the landing position of the sheet on the staple tray 44 can be
prevented because of the low rotation speed a of the rotation
roller 46a, so that the accuracy of rear-end alignment by the
contact with the rear end stopper 48 can be improved.
As a result, it is possible to improve alignment accuracy of a
sheet bundle on the staple tray 44, enabling to improve
post-processing accuracy.
The above-described stack operation is performed on the first
sheet. When sheets are stacked on the staple tray 44, a timing at
which the rotation roller 46a comes in contact with the stacking
surface is changed. To prevent reduction in the accuracy caused by
a change in the timing, at least one of the predetermined times t1
and t2 is changed for each number of stacked sheets. By doing so,
it is possible to obtain the same alignment accuracy as the first
sheet, with respect to the other sheets.
For the same purpose, it may be possible to change the
predetermined times t1 and t2 depending on a sheet type (thickness
or the like) that is set or detected.
Furthermore, it may be possible to provide a stack height detecting
unit that detects a height of a stack of sheets on the staple tray
44, and change the predetermined times t1 and t2 based on detection
information obtained from the stack height detecting unit. As the
stack height detecting unit, for example, it may be possible to
arrange a reflective optical sensor 68 on the upper surface of the
rear end stopper 48 and detect a height of a stack that is changed
depending on the number of stacked sheets.
As the stack height detecting unit, it may be possible to use a
mechanical detecting unit, which is conventionally used to detect a
height of a stack on a paper ejection tray.
FIG. 8 illustrates a second embodiment. The same components as
those of the above-described first embodiment are denoted by the
same symbols, the explanation of the same configurations and
functions will be omitted, and only main parts will be described
below (the same applies to the other embodiments to be described
later).
If the low rotation speed a is rapidly changed to the high rotation
speed b, a sheet surface may be damaged depending on a material of
the sheet. The second embodiment is conceived to cope with this
matter.
To cope with the above-described matter, in the second embodiment,
the rotation speed of the rotation roller 46a is changed to a
rotation speed c that is higher than the rotation speed a and lower
than the rotation speed b for a predetermined time t3 before the
end of the predetermined time t2.
Consequently, it is possible to increase the rotation speed of the
rotation speed b in a stepwise manner, so that it is possible to
reduce a gap that occurs when the rotation speed a is increased to
the rotation speed b.
The rotation speed of the rotation roller 46a is not rapidly
increased, so that it is possible to reduce the possibility that
the sheet surface is damaged by contact with the rotation roller
46a.
FIG. 9A to FIG. 10B illustrate a third embodiment of the present
invention.
The rotation speed b, as the rotation speed after stacking for
conveyance toward the rear end stopper 48 by the tapping roller 46,
is generally set to an optimal value based on sheet information. In
reality, a user inputs information, such as a thickness or strength
of a sheet, and the rotation speed b is automatically set based on
the information.
When the information is manually input, it is cumbersome to set the
input, and an input error may occur. If a type of a sheet to be
actually used and the input information do not match each other, a
sheet surface may be damaged or an alignment failure due to a
conveyance failure may occur.
The third embodiment is conceived to cope with the above-described
matters.
As illustrated in FIG. 9A, the rotation roller 46a of the tapping
roller 46 is arranged opposite to the supporting roller 56a of the
belt conveying unit 56, and the returning roller 50 is arranged
opposite to the supporting roller 56b of the belt conveying unit
56.
In the third embodiment, a combination of the rotation roller 46a
and the supporting roller 56a corresponds to the configuration for
ejecting paper by the the paper ejection roller 62 and the driven
roller 64 as illustrated in FIG. 1.
On the inner side of the endless belt 56c of the belt conveying
unit 56, a reflective sheet detection sensor 70 as a sheet
detecting unit that detects a sheet is arranged between the
rotation roller 46a and the returning roller 50.
In a supporting portion of the returning roller 50, a deflection
detecting unit 72 that detects deflection of a sheet is arranged.
The deflection detecting unit 72 includes a contact, one end of
which is supported and which is rotatable in a vertical direction,
and includes a detection sensor that detects a rotation angle of
the contact. In the third embodiment, a predetermined amount of
deflection (height of deflection) of a sheet is detected.
A leading end of a first sheet 66a conveyed onto the staple tray 44
by the intermediate conveying roller pair 40 is nipped between the
rotation roller 46a of the tapping roller 46 and the belt 56c, and
the sheet 66a is conveyed to the paper ejection tray 60 side by the
rotation roller 46a rotating clockwise.
The tapping roller 46 can be separated from the opposing supporting
roller 56a, and can change a conveying force of the rotation roller
46a by changing a contact pressure of the rotation roller 46a
against the supporting roller 56a.
When the sheet 66a is conveyed by a predetermined distance to the
paper ejection tray 60 side by the rotation roller 46a, as
illustrated in FIG. 9B, the rotation roller 46a rotates in a
reverse direction to convey the sheet 66a toward the rear end
stopper 48.
The above-described predetermined distance is different for each
sheet size, and is set to a time (distance) from when the rear end
of the sheet 66a passes through the nip of the intermediate
conveying roller pair 40 (a time at which the intermediate
conveying sensor 42 detects the rear end) to when the rear end of
the sheet 66a remains between the nip of the rotation roller
46a.
If productivity is taken into account, it is desirable to set the
predetermined distance to a value close to a distance at which the
rear end of the sheet 66a passes through the nip of the
intermediate conveying roller pair 40.
When the sheet 66a is conveyed by the rotation roller 46a, the
sheet detection sensor 70 detects the rear end of the sheet 66a
(FIG. 9C). When the sheet 66a is further conveyed, the rear end of
the sheet 66a butts against the nip of the returning roller 50, the
rotation of which is stopped, and a rear end portion of the sheet
66a is deflected.
When the deflection detecting unit 72 detects a predetermined
amount of deflection, the rotation roller 46a stops and the sheet
conveyance is stopped, so that the sheet can be stopped such that
the position of the rear end of the sheet is accurately located at
a nip position of the returning roller 50, without the influence of
fluctuation in the sheet conveyance or damage on the sheet
depending on each paper type, each paper, or a difference in the
environment or the like (FIG. 9D).
If a detection height to be detected by the deflection detecting
unit 72 is too low, error detection may occur when a large number
of papers are set on the staple tray. In contrast, if the detection
height is too high, paper may be damaged due to deflection.
Therefore, it is desirable to set the detection height of the
deflection detecting unit 72 in a range in which error detection
does not occur even when a large number of papers are set and in
which paper is not damaged due to deflection.
A time from when the sheet detection sensor 70 detects the rear end
of the sheet to when the deflection detecting unit 72 detects
occurrence of a predetermined amount of deflection on the sheet is
measured (determined).
Assuming that a measured time is denoted by t and predetermined
values t.sub.1 and t.sub.2 have a relationship such that
t.sub.1<t.sub.2, it is determined that the sheet 66a is thin
paper when a paper thickness is such that t<t.sub.1, plain paper
when the paper thickness is such that t.sub.1.ltoreq.t<t.sub.2,
and thick paper when the paper thickness is such that
t.sub.2.ltoreq.t.
Subsequently, the conveying force of the rotation roller 46a with
respect to the sheet conveyed to the staple tray 44 by the
intermediate conveying roller pair 40 is adjusted such that the
conveying force is reduced when the sheet is thin paper and
increased when the sheet is thick paper, so that it becomes
possible to switch to optimal control, such as control to prevent
damage on the thin paper or control to prevent a sheet feed failure
of the thick paper, without input of paper information from a
user.
In the third embodiment, the control is switched by using the two
predetermined values t.sub.1 and t.sub.2. However, the number of
the predetermined values t.sub.0 for switching the control may be
one or three or more.
When the deflection detecting unit 72 detects occurrence of a
predetermined amount of deflection of the sheet 66a, the rotation
roller 46a of the tapping roller 46 stops conveyance and is
separated from the supporting roller 56a.
When the rotation roller 46a is separated, a press of one side of
the deflected sheet 66a is released and the deflection is returned
because of the hardness of the sheet 66a (FIG. 9E).
After the rotation roller 46a is separated, the returning roller 50
conveys the sheet 66a and causes the sheet 66a to butt against the
rear end stopper 48 serving as a reference fence (FIG. 9F).
Because of the deflection generated as illustrated in FIG. 9D, the
rear end of the sheet 66a is accurately stopped at the nip position
of the returning roller 50. Therefore, it is possible to accurately
align the sheet with respect to the rear end stopper 48.
FIGS. 10A and 10B illustrate a stack operation of a second sheet
66b.
A conveying force (the rotation speed b after stacking) of the
rotation roller 46a of the tapping roller 46 is adjusted to an
optimal value in accordance with the paper thickness calculated for
the first sheet 66a.
When the sheet 66b is conveyed by a predetermined distance by the
rotation roller 46a as illustrated in FIG. 10A, the rotation roller
46a rotates in a reverse direction and conveys the sheet 66b toward
the rear end stopper 48 as illustrated in FIG. 10B.
Similarly to the first sheet, when the sheet 66b is conveyed by the
rotation roller 46a, the rear end of the sheet 66b butts against
the nip of the returning roller 50, the rotation of which is
stopped, and a rear end portion of the sheet 66b is deflected. When
the deflection detecting unit 72 detects a predetermined amount of
deflection, the rotation roller 46a stops and the conveyance of the
sheet 66b is stopped.
The rear ends of the second and subsequent sheets to be subjected
to the binding process are also accurately stopped at the nip
position of the returning roller 50. Therefore, it is possible to
accurately align the sheets with respect to the rear end stopper
48.
If paper, such as plain paper or thick paper, that has certain
hardness and is less likely to be damaged when butted against the
nip of the returning roller 50 is fed, it may be possible to
increase the conveying speed (rotation speed) of the rotation
roller 46a to improve the productivity.
FIGS. 11A to 11C illustrate a fourth embodiment of the present
invention.
In the third embodiment, the sheet detection sensor 70 is arranged
below the stacking surface of the staple tray 44, and therefore, it
is difficult to detect the rear ends of the second and subsequent
sheets. In this case, the rotation speed of the rotation roller 46a
is adjusted based on a detection result of the amount of deflection
of the first sheet, and the rotation speed is maintained constant
in a single job.
In the fourth embodiment, as illustrated in FIGS. 11A, 11B, and
11C, a sheet detection sensor 74 is arranged above the stacking
surface of the staple tray 44 in order to detect the amount of
deflection for each sheet.
Even for the second sheet 66b and subsequent sheet, a time from
when the sheet detection sensor 74 detects the rear end of the
sheet to when the deflection detecting unit 72 detects a
predetermined amount of deflection is measured, and the conveying
force and the conveying speed of the rotation roller 46a are
optimized.
As illustrated in FIG. 11A, when the first sheet 66a is conveyed
toward the rear end stopper 48 by the rotation roller 46a, the
sheet detection sensor 74 detects the rear end of the sheet 66a.
The conveying force and the conveying speed of the rotation roller
46a are adjusted to optimal values in accordance with a paper
thickness calculated for the first sheet 66a.
If the sheet detection sensor 74 is a transmissive paper detection
sensor, it is only possible to detect presence or absence of a
sheet, and it is difficult to accurately detect the rear ends of
the second sheet 66b and subsequent sheet. Therefore, in the fourth
embodiment, a sensor, such as an ultrasonic sensor, that can detect
the rear end of paper from a change in the thickness is used as the
sheet detection sensor 74.
When the sheet 66a is conveyed by the rotation roller 46a, the rear
end of the sheet 66a butts against the nip of the returning roller
50, the rotation of which is stopped, and a rear end portion of the
sheet 66a is deflected. When the deflection detecting unit 72
detects a predetermined amount of deflection, the rotation roller
46a stops and the conveyance of the sheet 66a is stopped, so that
the sheet can be stopped such that the position of the rear end of
the sheet is accurately located at the nip position of the
returning roller 50, without the influence of fluctuation in the
sheet conveyance or damage on the sheet depending on each paper
type, each paper, or a difference in the environment or the like
(FIG. 11B). This operation for accurate alignment of the rear end
of the sheet is similarly performed to the second sheet 66b that is
conveyed next as illustrated in FIG. 11C.
A time from when the sheet detection sensor 74 detects the rear end
of the sheet to when the deflection detecting unit 72 detects
occurrence of a predetermined amount of deflection is measured.
Assuming that a measured time of the first sheet 66a is denoted by
t.sub.1, a measured time of the second sheet 66b is denoted by
t.sub.2, . . . , and predetermined values s.sub.1 and s.sub.2 have
a relationship such that s.sub.1<s.sub.2, it is determined that
paper is thin paper when a paper thickness is such that
(t.sub.1+t.sub.2+ . . . t.sub.n)/n<s.sub.1, plain paper when the
paper thickness is such that s.sub.1.ltoreq.(t.sub.1+t.sub.2+ . . .
t.sub.n)/n<s.sub.2, and thick paper when the paper thickness is
such that s.sub.2.ltoreq.(t.sub.1+t.sub.2+ . . . t.sub.n)/n.
Subsequently, the conveying force of the returning roller 50 with
respect to the sheet conveyed toward the rear end stopper 48 by the
rotation roller 46a is adjusted such that the conveying force is
reduced when the paper is thin paper and increased when the paper
is thick paper, so that it becomes possible to prevent erroneous
detection of the paper thickness due to sudden fluctuation in the
measured time t.sub.n.
Consequently, it becomes possible to switch to optimal control,
such as control to prevent damage on the thin paper or control to
prevent a sheet feed failure of the thick paper, without input of
paper information from a user.
Furthermore, if paper, such as plain paper or thick paper, that has
certain hardness and is less likely to be damaged when butted
against the nip of the returning roller 50 is fed, it may be
possible to increase the conveying speed of the rotation roller 46a
to improve the productivity.
In the fourth embodiment, the control is switched by using the two
predetermined values s.sub.1 and s.sub.2. However, the number of
the predetermined values s.sub.n for switching the control may be
one or three or more. Moreover, it may be possible to use a method
of determining a threshold for the value t.sub.n in each case,
without using the value s.
FIGS. 12A and 12B illustrate a fifth embodiment of the present
invention.
A feature of the fifth embodiment is in that paper type
information, which is determined based on a time taken to detect a
predetermined amount of deflection on the staple tray 44, is used
to optimize a conveying force of a returning member for stacking a
sheet on the paper ejection tray 60.
As illustrated in FIG. 12A, a returning roller 80 as a returning
member, which returns a sheet bundle 76 discharged on the paper
ejection tray 60 to the upstream side in a discharging direction
and causes the sheet bundle 76 to butt against an end fence 78, is
provided below the supporting roller 56a, that is a driving roller,
so as to move back and force. A reference sign 82 denotes a paper
surface detection sensor that detects a height of the sheet bundle
76 discharged on the paper ejection tray 60. The paper ejection
tray 60 is moved up and down based on detection information
obtained by the paper surface detection sensor 82.
The sheet bundle 76 is discharged on the paper ejection tray 60 by
the rotation roller 46a and the belt conveying unit 56. The
conveying force of the rotation roller 46a is adjusted to an
optimal value in accordance with a paper thickness calculated
through deflection detection on the staple tray 44.
As illustrated in FIG. 12B, the sheet bundle 76 discharged on the
paper ejection tray 60 is caused to butted against the end fence 78
by the returning roller 80, and aligned in the discharging
direction.
The returning roller 80 can change the conveying force by changing
a contact pressure against the paper surface, and the conveying
force thereof is adjusted to an optimal value in accordance with a
paper thickness calculated on the staple tray 44. For example, by
reducing the conveying force in the case of thin paper and
increasing the conveying force in the case of thick paper, it is
possible to align sheets while maintaining the paper quality.
An operation performed after a sheet butts against the rear end
stopper 48 in each of the above-described embodiments will be
described below.
FIG. 13 illustrates a state in which the sheets 66 are stacked in
an aligned manner on the staple tray 44.
As illustrated in FIG. 14, the jogger fences 52 arranged on left
and right sides of the staple tray 44 are moved in the sheet width
direction perpendicular to the sheet conveying direction, by a rack
and pinion mechanism.
As illustrated in FIG. 15A, after the first sheet 66a conveyed to
the staple tray 44 is deflected by a portion of the returning
roller 50, the rear end of the sheet 66a is butted against the rear
end stopper 48 by the returning roller 50 (FIG. 15B). Subsequently,
the jogger fences 52 move so as to come closer to each other in a
width direction of the sheet 66a and align the sheet in the width
direction (FIG. 15C).
As described above, at the stage illustrated in FIG. 15A, a time
from when the sheet detection sensor 70 detects the leading end of
the sheet 66a to when the deflection detecting unit 72 detects
occurrence of a predetermined amount of deflection is measured, and
a thickness of the sheet 66a is determined based on the measured
time t.
The moving speed of the jogger fences 52 is increased in the case
of thick paper to improve the productivity, and the moving speed of
the jogger fences 52 is decreased in the case of thin paper.
By doing so, it is possible to reduce damage due to the contact of
the jogger fences 52 with the sheet 66a, and prevent reduction in
the paper quality.
As illustrated in FIG. 15D, when alignment in the sheet width
direction is finished, the jogger fences 52 are moved away, and the
same operation is repeated for the subsequent sheets 66b (FIG.
15E).
A punching operation performed by the punching unit 16 will be
described based on FIGS. 16A to 16D.
As illustrated in FIG. 16A, the sheet 66, on which an image is
formed by the image forming apparatus 4, is conveyed to the sheet
post-processing apparatus 6 by the entrance roller pair 12. As
illustrated in FIG. 16B, the sheet 66 stops while the leading end
of the sheet 66 is sandwiched by the conveying roller pair 18.
As illustrated in FIG. 16C, a punching pin 16a of the punching unit
16 is moved downward while the sheet 66 is stopped, and a hole is
punched in the sheet 66.
A force (velocity) at the time of punching is adjusted based on
information on a paper thickness obtained through the
above-described deflection detection. In general, a large sound
occurs when a punching force is large. However, by reducing the
force with respect to thin paper for which the punching force is
not needed, it is possible to reduce the sound at the time of
punching.
As illustrated in FIG. 16D, the punching pin 16a is moved away
after punching, and conveyance of the sheet 66 toward the staple
tray 44 is started.
In the above-described embodiments, a change in the conveying force
of the rotation roller 46a or the returning roller 50 according to
the condition, such as the paper thickness, is described as a
change in the rotation speed. However, this may be realized by
changing a contact pressure between the rotation roller 46a or the
returning roller 50 and an opposing member.
While the preferred embodiments of the present invention have been
explained above, the present invention is not limited to the
specific embodiments, and various modifications and changes may be
made within the scope of the appended claims unless otherwise
specified in this document.
The effects described in relation to the embodiments of the present
invention are examples of the most preferred effects, and not
limited to those described in the embodiments.
According to the embodiments of the present invention, it is
possible to provide a sheet post-processing apparatus capable of
stabilizing a landing state of a sheet on a stack tray, and
contributing to sheet alignment accuracy and post-processing
accuracy.
Although the invention has been described with respect to specific
embodiments for a complete and clear disclosure, the appended
claims are not to be thus limited but are to be construed as
embodying all modifications and alternative constructions that may
occur to one skilled in the art that fairly fall within the basic
teaching herein set forth.
* * * * *